ABSTRACT
Spread spectrum (SS) was first used by the military to prevent jamming. It now covers secure digital communications, commercial and industrial purposes as well. A SS receiver uses a locally generated replica pseudo noise code and a correlator receiver to separate only the desired coded information from all possible signals. A SS correlator can be thought of as a very special matched filter. A typical commercial direct sequence radio might have a processing gain of from 11 to 16 dB, depending on data rate. It can tolerate total jammer power levels of from 11 to 16 dB stronger than the desired signal. Demodulation of spread spectrum is called despreading. This is basically a restoration of the base band signal bandwidth and energy to what they were before SS operation. A further analysis of interference cancellation by spread spectrum is necessary. The effect of the orthogonal channelization is to reduce the mutual interference between users.
